1. Field of the Invention
This invention relates to exhaust systems for gas turbine engines in which a considerable amount of energy is present in the exhaust gas. This energy, largely heat, may be usefully employed, for example in combined heat and power systems. In such a system the engine is used as a prime mover to generate electricity and the exhaust gas is passed through a heat exchanger to generate steam or to recover otherwise heat energy from the exhaust gas.
2. Description of the Related Art
It is often a requirement in such systems that the production of steam is controllable by the amount of hot exhaust gas allowed through the heat exchanger, surplus gas being diverted through a bypass arrangement to atmosphere by way of a stack.
Conventional bypass arrangements commonly employ a main duct and a bypass duct branching from it at right angles. A valve at the branch either allows the exhaust gas to proceed axially along the main duct or diverts some or all of it to the bypass duct. This diversion of the exhaust gas causes considerable disturbance of the flow and the resultant adverse forces generated can degrade turbine peformance and may even cause premature turbine blade or ducting failure.
Such repercussions of flow disturbance on turbine performance can be alleviated at least partially by increasing the length of the duct sections, particularly between the engine outlet and the bypass section. Such increase in overall dimensions is not always possible and is in any event undesirable.